Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/52—Separators
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
  • C09D133/24—Homopolymers or copolymers of amides or imides
  • C09D133/26—Homopolymers or copolymers of acrylamide or methacrylamide
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D125/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Coating compositions based on derivatives of such polymers
  • C09D125/02—Homopolymers or copolymers of hydrocarbons
  • C09D125/04—Homopolymers or copolymers of styrene
  • C09D125/08—Copolymers of styrene
  • C09D125/14—Copolymers of styrene with unsaturated esters
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
  • C09D133/18—Homopolymers or copolymers of nitriles
  • C09D133/20—Homopolymers or copolymers of acrylonitrile
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D147/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds; Coating compositions based on derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/18—Fireproof paints including high temperature resistant paints
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
  • H01M50/42—Acrylic resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/431—Inorganic material
  • H01M50/434—Ceramics
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/443—Particulate material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
  • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present disclosure relates to a composition for an electrochemical device functional layer, a laminate for an electrochemical device, and an electrochemical device.
• Electrochemical devices such as lithium ion secondary batteries and electric double-layer capacitors have characteristics such as compact size, light weight, high energy-density, and the ability to be repeatedly charged and discharged, and are used in a wide variety of applications.
• a lithium ion secondary battery normally includes battery members such as a positive electrode, a negative electrode, and a separator that isolates the positive electrode and the negative electrode from each other and prevents short-circuiting between the positive and negative electrodes.
• Constituent members that include a functional layer such as a heat-resistant layer aimed at improving heat resistance of the constituent member or an adhesive layer aimed at improving adhesiveness between constituent members are used in electrochemical devices such as lithium ion secondary batteries.
• electrodes that further include a functional layer formed on an electrode substrate in which an electrode mixed material layer is provided on a current collector and separators that include a functional layer formed on a separator substrate are used as battery members.
• a functional layer such as described above is formed by applying a composition for a secondary battery functional layer onto a substrate such as a separator substrate and then drying a coating film on the substrate.
• further improvements to functional layers have been studied with the aim of further increasing the performance of electrochemical devices such as lithium ion secondary batteries.
• adhesiveness required of a functional layer may, for example, be adhesiveness before immersion in electrolyte solution (hereinafter, also referred to as “dry adhesiveness”), adhesiveness after immersion in electrolyte solution (hereinafter, also referred to as “wet adhesiveness”), etc.
• one object of the present disclosure is to provide a composition for an electrochemical device functional layer that can form a functional layer having excellent adhesiveness.
• Another object of the present disclosure is to provide a laminate for an electrochemical device that includes a functional layer obtained using this composition for an electrochemical device functional layer and an electrochemical device that includes this laminate for an electrochemical device.
• the inventor made diligent studies to achieve the objects set forth above.
• the inventor reached a new finding that it is possible to form a functional layer having excellent adhesiveness by using a composition for a functional layer that contains a particulate polymer (X) and a particulate polymer (Y) having a smaller volume-average particle diameter than the particulate polymer (X) and in which one of the particulate polymer (X) and the particulate polymer (Y) includes a specific reactive monomer unit A while the other of the particulate polymer (X) and the particulate polymer (Y) includes a specific reactive monomer unit B.
• the inventor completed the present disclosure.
• composition for a functional layer that contains a particulate polymer (X) and a particulate polymer (Y) having a smaller volume-average particle diameter than the particulate polymer (X) and in which one of the particulate polymer (X) and the particulate polymer (Y) includes the specific reactive monomer unit A set forth above while the other of the particulate polymer (X) and the particulate polymer (Y) includes the specific reactive monomer unit B set forth above in this manner, it is possible to form a functional layer having excellent adhesiveness.
• (meth)acryl indicates “acryl” and/or “methacryl”.
• An "epoxy group-containing monomer unit” included in one particulate polymer among the particulate polymer (X) and the particulate polymer (Y) is treated as the "reactive monomer unit A" in the present disclosure in a case in which the other particulate polymer among the particulate polymer (X) and the particulate polymer (Y) does not include a hydroxy group-containing monomer unit as the reactive monomer unit A and is treated as the "reactive monomer unit B" in the present disclosure in a case in which the other particulate polymer among the particulate polymer (X) and the particulate polymer (Y) does include a hydroxy group-containing monomer unit as the reactive monomer unit A.
• volume-average particle diameters of the particulate polymers (X) and (Y) referred to in the present disclosure can be measured by a method described in the EXAMPLES section of the present specification. Moreover, it is possible to judge that a composition for a functional layer contains a particulate polymer (X) and a particulate polymer (Y) having a smaller volume-average particle diameter than the particulate polymer (X) by, for example, observing a peak corresponding to the particulate polymer (X) at a large particle diameter side and a peak corresponding to the particulate polymer (Y) at a small particle diameter side in a particle diameter distribution (by volume) measured by laser diffraction.
• the volume-average particle diameter of the particulate polymer (X) is preferably not less than 1 ⁇ m and not more than 10 ⁇ m.
• volume-average particle diameter of the particulate polymer (X) is within the specific range set forth above, adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved, and heat resistance of the functional layer can also be improved.
• (meth)acrylic acid alkyl ester as used in the present disclosure is not inclusive of “(meth)acrylic acid cycloalkyl esters".
• an "alkyl group” that is included in a (meth)acrylic acid alkyl ester is a chain (linear or branched) saturated hydrocarbon group
• a "cycloalkyl group” i.e., a cyclic saturated hydrocarbon group
• alkyl group i.e., a cyclic saturated hydrocarbon group
• the particulate polymer (Y) preferably includes either or both of an aromatic monovinyl monomer unit and a (meth)acrylic acid alkyl ester monomer unit.
• adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved while also sufficiently ensuring the presence of voids between components in the functional layer, increasing air permeability of the functional layer, and improving ion conductivity of the functional layer to thereby enable improvement of output characteristics of an electrochemical device that includes the functional layer.
• composition for an electrochemical device functional layer preferably further comprises non-conductive heat-resistant particles.
• composition for a functional layer further contains non-conductive heat-resistant particles, heat resistance of a functional layer can be improved by using the composition for a functional layer.
• content of the particulate polymer (Y) is preferably not less than 0.5 parts by mass and not more than 6 parts by mass per 100 parts by mass of the non-conductive heat-resistant particles.
• adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved while also sufficiently ensuring the presence of voids between components in the functional layer, increasing air permeability of the functional layer, and improving ion conductivity of the functional layer to thereby enable improvement of output characteristics of an electrochemical device that includes the functional layer.
• a presently disclosed laminate for an electrochemical device comprises: a substrate; and a functional layer for an electrochemical device formed on the substrate, wherein the functional layer for an electrochemical device is obtained using the composition for an electrochemical device functional layer according to any one of the foregoing [1] to [7].
• a ratio of the volume-average particle diameter of the particulate polymer (X) relative to thickness of a non-conductive heat-resistant particle layer formed of non-conductive heat-resistant particles is preferably not less than 0.8 and not more than 10.
• a non-conductive heat-resistant particle layer referred to in the present disclosure can be measured by a method described in the EXAMPLES section of the present specification.
• a presently disclosed electrochemical device comprises the laminate for an electrochemical device according to the foregoing [8] or [9].
• An electrochemical device such as set forth above can display excellent electrochemical characteristics (for example, cycle characteristics and output characteristics).
• composition for an electrochemical device functional layer that can form a functional layer having excellent adhesiveness.
• composition for an electrochemical device functional layer (hereinafter, also referred to simply as a "composition for a functional layer”) can be used as a material in formation of a functional layer that is included in the presently disclosed laminate for an electrochemical device (hereinafter, also referred to simply as a "laminate").
• laminate for an electrochemical device can be used in production of the presently disclosed electrochemical device.
• the presently disclosed composition for a functional layer can optionally further contain non-conductive heat-resistant particles, an amine compound, and other components besides the particulate polymer (X) and the particulate polymer (Y) described above.
• the presently disclosed composition for a functional layer can, for example, be a slurry composition having the particulate polymer (X) and the particulate polymer (Y) dispersed in a dispersion medium such as water.
• one of the particulate polymer (X) and the particulate polymer (Y) includes a reactive monomer unit A while the other of the particulate polymer (X) and the particulate polymer (Y) includes a reactive monomer unit B.
• the particulate polymer (X) includes at least one among the reactive monomer unit A and the reactive monomer unit B while the particulate polymer (Y) includes at least the other among the reactive monomer unit A and the reactive monomer unit B.
• the reactive monomer unit A is an epoxy group-containing monomer unit or a hydroxy group-containing monomer unit.
• the particulate polymer (X) includes an epoxy group-containing monomer unit as the reactive monomer unit A
• the particulate polymer (X) includes a hydroxy group-containing monomer unit as the reactive monomer unit A
• the particulate polymer (Y) includes an epoxy group-containing monomer unit as the reactive monomer unit A
• the particulate polymer (Y) does not include a hydroxy group-containing monomer unit as the reactive monomer unit A, though no specific limitations are made.
• the particulate polymer (Y) includes a hydroxy group-containing monomer unit as the reactive monomer unit A
• epoxy group-containing monomers may be used individually, or two or more of these epoxy group-containing monomers may be used in combination in a freely selected ratio.
• unsaturated glycidyl ethers and glycidyl esters of unsaturated carboxylic acids are preferable, allyl glycidyl ether and glycidyl methacrylate are more preferable, and glycidyl methacrylate is even more preferable as an epoxy group-containing monomer.
• one of these hydroxy group-containing monomers may be used individually, or two or more of these hydroxy group-containing monomers may be used in combination in a freely selected ratio.
• alkanol esters of ethylenically unsaturated carboxylic acids are preferable, and 4-hydroxybutyl acrylate, 1,4-cyclohexanedimethanol monoacrylate, and 2-hydroxy-3-phenoxypropyl acrylate are more preferable as hydroxy group-containing monomers.
• (meth)acrylamide group-containing monomers that include a hydroxyalkyl group, such as N-methylol (meth)acrylamide, are considered to not be included among hydroxy group-containing monomers.
• (meth)allyl indicates “allyl” and/or “methallyl”.
• the reactive monomer unit B is a monomer unit that can react with the reactive monomer unit A to form a bond. Moreover, the type of reactive monomer unit B is selected in accordance with the type of reactive monomer unit A.
• the reactive monomer unit B (hereinafter, also referred to as a "reactive monomer unit B1" in this case) is required to include one or more selected from the group consisting of a (meth)acrylamide group-containing monomer unit, an acid anhydride monomer unit, a sulfo group-containing monomer unit, a phosphate group-containing monomer unit, and an amino group-containing monomer unit.
• the reactive monomer unit B1 may optionally further include a carboxy group-containing monomer unit.
• the particulate polymer (Y) includes the reactive monomer unit B1
• stability during production of the particulate polymer (Y) can be improved through the particulate polymer (Y) further including a carboxy group-containing monomer unit as the reactive monomer unit B1.
• the reactive monomer unit B1 does not normally include a monomer unit other than the aforementioned (meth)acrylamide group-containing monomer unit, acid anhydride monomer unit, sulfo group-containing monomer unit, phosphate group-containing monomer unit, amino group-containing monomer unit, and carboxy group-containing monomer unit, though no specific limitations are made.
• R 3 in the preceding formula is preferably a hydrogen atom, an alkyl group having a carbon number of not less than 1 and not more than 10, or a hydroxyalkyl group having a carbon number of not less than 1 and not more than 10, more preferably a hydrogen atom, an alkyl group having a carbon number of not less than 1 and not more than 5, or a hydroxyalkyl group having a carbon number of not less than 1 and not more than 5, and even more preferably a hydrogen atom.
• Examples of (meth)acrylamide group-containing monomers that can form a (meth)acrylamide group-containing monomer unit include (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N-methylol(meth)acrylamide.
• acrylamide is preferable as a (meth)acrylamide group-containing monomer.
• one of these acid anhydride monomers may be used individually, or two or more of these acid anhydride monomers may be used in combination in a freely selected ratio.
• maleic anhydride is preferable as an acid anhydride monomer.
• the particulate polymer (Y) includes either or both of an aromatic monovinyl monomer unit and a (meth)acrylic acid alkyl ester monomer unit as another monomer unit.
• a particulate polymer (Y) that can suitably be used in the presently disclosed composition for a functional layer may include at least a (meth)acrylic acid alkyl ester monomer unit, a nitrile group-containing monomer unit, and a cross-linkable monomer unit as other monomer units, may include at least an aromatic monovinyl monomer unit, a (meth)acrylic acid alkyl ester monomer unit, and a cross-linkable monomer unit as other monomer units, or may include an aromatic monovinyl monomer unit and a conjugated diene monomer unit as other monomer units, for example.
• the particulate polymer (Y) may or may not include monomer units other than the aforementioned reactive monomer unit A, reactive monomer unit B, aromatic monovinyl monomer unit, (meth)acrylic acid alkyl ester monomer unit, nitrile group-containing monomer unit, conjugated diene monomer unit, and cross-linkable monomer unit without any specific limitations.
• aromatic monovinyl monomers that can form an aromatic monovinyl monomer unit in the particulate polymer (Y) are the same as specific examples and preferable examples of aromatic monovinyl monomers that can form an aromatic monovinyl monomer unit in the particulate polymer (X) described above.
• the proportional content of an aromatic monovinyl monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% is preferably 10 mass% or more, more preferably 15 mass% or more, and preferably 25 mass% or more, and is preferably 60 mass% or less, more preferably 50 mass% or less, and even more preferably 40 mass% or less.
• n-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate are preferable, and n-butyl acrylate is more preferable as a (meth)acrylic acid alkyl ester monomer.
• the proportional content of a (meth)acrylic acid alkyl ester monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% is preferably 50 mass% or more, more preferably 55 mass% or more, and even more preferably 58 mass% or more, and is preferably 98 mass% or less, more preferably 97 mass% or less, and even more preferably 96 mass% or less.
• proportional content of a (meth)acrylic acid alkyl ester monomer unit in the particulate polymer (Y) may be 70 mass% or more, or may be 80 mass% or more, and may be 93 mass% or less, or may be 92 mass% or less.
• any ⁇ , ⁇ -ethylenically unsaturated compound that includes a nitrile group can be used as an ⁇ , ⁇ -ethylenically unsaturated nitrile monomer without any specific limitations.
• Examples include acrylonitrile; ⁇ -halogenoacrylonitriles such as ⁇ -chloroacrylonitrile and ⁇ -bromoacrylonitrile; and ⁇ -alkylacrylonitriles such as methacrylonitrile and ⁇ -ethylacrylonitrile.
• acrylonitrile is preferable as a nitrile group-containing monomer.
• one of these nitrile group-containing monomers may be used individually, or two or more of these nitrile group-containing monomers may be used in combination in a freely selected ratio.
• the proportional content of a nitrile group-containing monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, and is preferably 20 mass% or less, more preferably 15 mass% or less, and even more preferably 10 mass% or less.
• the proportional content of a nitrile group-containing monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% may be 2 mass% or more, may be 3 mass% or more, or may be 4 mass% or more, and may be 8 mass% or less, may be 6 mass% or less, or may be 4 mass% or less.
• 1,3-butadiene is preferable as a conjugated diene monomer.
• conjugated diene monomers may be used individually, or two or more of these conjugated diene monomers may be used in combination in a freely selected ratio.
• the proportional content of a conjugated diene monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% is preferably 30 mass% or more, more preferably 40 mass% or more, and even more preferably 50 mass% or more, and is preferably 80 mass% or less, more preferably 75 mass% or less, and even more preferably 70 mass% or less.
• cross-linkable monomers that can form a cross-linkable monomer unit in the particulate polymer (Y) are the same as specific examples and preferable examples of cross-linkable monomers that can form a cross-linkable monomer unit in the particulate polymer (X) described above.
• the proportional content of a cross-linkable monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% is preferably 0.05 mass% or more, more preferably 0.1 mass% or more, and even more preferably 0.15 mass% or more, and is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less.
• the proportional content of a cross-linkable monomer unit in the particulate polymer (Y) when all monomer units in the particulate polymer (Y) are taken to be 100 mass% may be 0.2 mass% or more, may be 0.5 mass% or more, may be 1 mass% or more, or may be 1.5 mass% or more, and may be 1.5 mass% or less, may be 1 mass% or less, may be 0.5 mass% or less, or may be 0.2 mass% or less.
• the glass-transition temperature of the particulate polymer (Y) is preferably -100°C or higher, more preferably -90°C or higher, and even more preferably -80°C or higher, and is preferably lower than 30°C, more preferably 20°C or lower, and even more preferably 15°C or lower.
• the glass-transition temperature of the particulate polymer (Y) is not lower than any of the lower limits set forth above, adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved, and blocking resistance of the functional layer can also be improved.
• the particulate polymer (Y) can be produced through polymerization of a monomer composition that contains the monomers described above, carried out in an aqueous solvent such as water, for example.
• the proportional content of each monomer in the monomer composition is normally the same as the proportional content of each monomer unit in the particulate polymer (Y) unless otherwise specified.
• the polymerization method and the polymerization reaction can be any of the polymerization methods and polymerization reactions that were given for the production method of the particulate polymer (X) described above, for example, without any specific limitations.
• the content of the particulate polymer (Y) in the composition for a functional layer is preferably 10 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 50 parts by mass or more, and further preferably 80 parts by mass or more per 100 parts by mass of the particulate polymer (X), and is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, even more preferably 150 parts by mass or less, and further preferably 120 parts by mass or less per 100 parts by mass of the particulate polymer (X).
• the content of the particulate polymer (Y) is not less than any of the lower limits set forth above, adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved, and heat resistance of the functional layer can also be improved.
• output characteristics of an electrochemical device that includes a functional layer formed using the composition for a functional layer can be improved because voids between components in the functional layer can be sufficiently ensured, air permeability of the functional layer can be increased, and ion conductivity of the functional layer can be improved.
• the content of the particulate polymer (Y) in the composition for a functional layer is even further preferably 95 parts by mass or more, yet further preferably 100 parts by mass or more, and particularly preferably 105 parts by mass or more per 100 parts by mass of the particulate polymer (X).
• the content of the particulate polymer (Y) in the composition for a functional layer is even further preferably 94 parts by mass or less, yet further preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less per 100 parts by mass of the particulate polymer (X).
• the content of the particulate polymer (Y) in the composition for a functional layer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and further preferably 2.5 parts by mass or more per 100 parts by mass of the non-conductive heat-resistant particles, and is preferably 6 parts by mass or less, more preferably 4.5 parts by mass or less, and even more preferably 4 parts by mass or less per 100 parts by mass of the non-conductive heat-resistant particles.
• the content of the particulate polymer (Y) is not less than any of the lower limits set forth above, adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved, and heat resistance of the functional layer can also be improved.
• output characteristics of an electrochemical device that includes a functional layer formed using the composition for a functional layer can be improved because voids between components in the functional layer can be sufficiently ensured, air permeability of the functional layer can be increased, and ion conductivity of the functional layer can be improved.
• composition for a functional layer preferably further contains non-conductive heat-resistant particles.
• heat resistance of a functional layer can be improved by using the composition for a functional layer.
• non-conductive heat-resistant particles refers to fine particles that have a heat-resistance temperature of 200°C or higher and that are not electrically conductive.
• heat-resistance temperature refers to a temperature at which substantial physical change such as thermal deformation does not occur.
• the non-conductive heat-resistant particles are preferably inorganic particles.
• inorganic particles have a comparatively large specific gravity, this makes it easier for the particulate polymer (X) to protrude relative to the inorganic particles at a thickness direction surface of a functional layer in a situation in which a functional layer is formed through application of the composition for a functional layer containing inorganic particles onto a substrate, for example, and, as a result, enables further improvement of adhesiveness of the functional layer.
• the material of the inorganic particles is preferably an electrochemically stable material that is stably present in the environment of use of an electrochemical device.
• the inorganic particles may be particles of an oxide such as aluminum oxide (alumina), hydrous aluminum oxide (boehmite (AlOOH)), gibbsite (Al(OH) 3 ), silicon oxide, magnesium oxide (magnesia), magnesium hydroxide, calcium oxide, titanium oxide (titania), barium titanate (BaTiO 3 ), zirconium oxide (ZrO), or alumina-silica complex oxide; particles of a nitride such as aluminum nitride or boron nitride; particles of covalently bonded crystals such as silicon or diamond; particles of sparingly soluble ionic crystals such as barium sulfate, calcium fluoride, or barium fluoride; or fine particles of clay such as talc or montmorillonite.
• an oxide such as aluminum oxide (alumina), hydrous aluminum oxide (
• aluminum oxide aluminum oxide, hydrous aluminum oxide (boehmite), magnesium hydroxide, and barium sulfate are more preferable, and aluminum oxide is even more preferable.
• These particles may be subjected to element substitution, surface treatment, solid solution treatment, or the like as necessary.
• one of these types of inorganic particles may be used individually, or two or more of these types of inorganic particles may be used in combination in a freely selected ratio.
• the volume-average particle diameter (D50) of the non-conductive heat-resistant particles is preferably 0.1 ⁇ m or more, more preferably 0.2 ⁇ m or more, and even more preferably 0.25 ⁇ m or more, and is preferably 1.5 ⁇ m or less, more preferably 1.0 ⁇ m or less, and even more preferably 1.0 ⁇ m or less.
• volume-average particle diameter of the non-conductive heat-resistant particles is not less than any of the lower limits set forth above, excessively dense packing of the non-conductive heat-resistant particles in a functional layer formed using the composition for a functional layer can be inhibited. This makes it possible to increase air permeability and improve ion conductivity of the functional layer, and thus can improve output characteristics of an electrochemical device including the functional layer.
• the non-conductive heat-resistant particles can pack with suitably high density in a functional layer formed using the composition for a functional layer. This makes it possible to cause the functional layer to display sufficient heat resistance even when the thickness of the functional layer is reduced. As a result, the thickness of an electrochemical device including the functional layer can be reduced while also increasing the capacity of the electrochemical device.
• a volume ratio of the non-conductive heat-resistant particles and the particulate polymer (X) (non-conductive heat-resistant particles/particulate polymer (X)) in the composition for a functional layer is preferably 40/60 or more, more preferably 50/50 or more, even more preferably 60/40 or more, further preferably 70/30 or more, even further preferably 75/25 or more, yet further preferably 80/20 or more, and particularly preferably 85/15 or more, and is preferably 99/1 or less, more preferably 97/3 or less, even more preferably 95/5 or less, and further preferably 92/8 or less.
• the volume ratio of the non-conductive heat-resistant particles and the particulate polymer (X) (non-conductive heat-resistant particles/particulate polymer (X)) in the composition for a functional layer is not less than any of the lower limits set forth above, heat resistance of a functional layer that is formed using the composition for a functional layer can be improved because the non-conductive heat-resistant particles are sufficiently present in the functional layer.
• the volume ratio of the non-conductive heat-resistant particles and the particulate polymer (X) (non-conductive heat-resistant particles/particulate polymer (X)) in the composition for a functional layer is not more than any of the upper limits set forth above, adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved because the particulate polymer (X) is sufficiently present in the functional layer.
• a mass ratio of the non-conductive heat-resistant particles and the particulate polymer (X) (non-conductive heat-resistant particles/particulate polymer (X)) in the composition for a functional layer is preferably 50/50 or more, more preferably 60/40 or more, even more preferably 70/30 or more, further preferably 80/20 or more, even further preferably 90/10 or more, and yet further preferably 95/5 or more, and is preferably 999/1 or less, more preferably 998/2 or less, even more preferably 995/5 or less, and further preferably 99/1 or less.
• the mass ratio of the non-conductive heat-resistant particles and the particulate polymer (X) (non-conductive heat-resistant particles/particulate polymer (X)) in the composition for a functional layer is not less than any of the lower limits set forth above, heat resistance of a functional layer that is formed using the composition for a functional layer can be improved because the non-conductive heat-resistant particles are sufficiently present in the functional layer.
• the mass ratio of the non-conductive heat-resistant particles and the particulate polymer (X) (non-conductive heat-resistant particles/particulate polymer (X)) in the composition for a functional layer is not more than any of the upper limits set forth above, adhesiveness of a functional layer that is formed using the composition for a functional layer can be further improved because the particulate polymer (X) is sufficiently present in the functional layer.
• a mass ratio of the content of the non-conductive heat-resistant particles and the total content of the particulate polymer (X) and the particulate polymer (Y) (non-conductive heat-resistant particles/particulate polymers (X) and (Y)) in the composition for a functional layer is preferably 40/60 or more, more preferably 50/50 or more, even more preferably 60/40 or more, further preferably 70/30 or more, even further preferably 85/15 or more, yet further preferably 90/10 or more, and particularly preferably 93/7 or more, and is preferably 999/1 or less, more preferably 998/2 or less, even more preferably 995/5 or less, and further preferably 99/1 or less.
• air permeability of a functional layer that is formed using the composition for a functional layer can be increased and ion conductivity of the functional layer can be improved as a result of the total content of the particulate polymer (X) and the particulate polymer (Y) being suitably low, which enables improvement of output characteristics of an electrochemical device including the functional layer.
• the composition for a functional layer may contain any other components besides the particulate polymer (X), the particulate polymer (Y), the non-conductive heat-resistant particles, and the amine compound.
• any other components besides the particulate polymer (X), the particulate polymer (Y), the non-conductive heat-resistant particles, and the amine compound.
• known additives such as dispersants, viscosity modifiers, and wetting agents may be used as other components.
• One of these other components may be used individually, or two or more of these other components may be used in combination.
• the composition for a functional layer can be produced by mixing the above-described particulate polymer (X), the above-described particulate polymer (Y), water serving as a dispersion medium, and the non-conductive heat-resistant particles, amine compound, and other components that are used as necessary.
• the particulate polymer (X) or the particulate polymer (Y) is produced through polymerization of a monomer composition in an aqueous solvent
• the particulate polymer (X) or particulate polymer (Y) may be mixed with other components while still in the form of a water dispersion.
• water in the water dispersion may be used as the dispersion medium.
• the presently disclosed laminate for an electrochemical device includes a substrate and a functional layer formed on the substrate, wherein the functional layer is obtained using the presently disclosed composition for an electrochemical device functional layer. Since the presently disclosed composition for an electrochemical device functional layer can form a functional layer having excellent adhesiveness, a laminate that includes a functional layer obtained using the presently disclosed composition for an electrochemical device functional layer can improve electrochemical characteristics (for example, output characteristics and cycle characteristics) of an electrochemical device that includes the laminate for an electrochemical device.
• the substrate may be a separator substrate in a case in which the functional layer is used as a member that constitutes part of a separator and may be an electrode substrate obtained by forming an electrode mixed material layer on a current collector in a case in which the functional layer is used as a member that constitutes part of an electrode.
• the functional layer may be formed on a separator substrate or the like, and then the resultant laminate may be used in that form as an electrochemical device member such as a separator, or the functional layer may be formed on an electrode substrate, and then the resultant laminate may be used in that form as an electrode.
• the electrode substrate (positive electrode substrate or negative electrode substrate) on which the functional layer is formed is not specifically limited and may be an electrode substrate that is obtained by forming an electrode mixed material layer on a current collector.
• the current collector, components in the electrode mixed material layer for example, an electrode active material (positive electrode active material or negative electrode active material) and a binder for an electrode mixed material layer (binder for a positive electrode mixed material layer or binder for a negative electrode mixed material layer)
• the method by which the electrode mixed material layer is formed on the current collector can be known examples thereof such as any of those described in JP2013-145763A , for example.
• the electrode substrate may include any layer other than the functional layer that has an expected function in part thereof.
• the functional layer can be formed on the above-described substrate using the presently disclosed composition for a functional layer.
• the functional layer contains at least the above-described particulate polymer (X) and particulate polymer (Y) and also contains the non-conductive heat-resistant particles, amine compound, and other components that are used as necessary.
• components contained in the functional layer are components that were contained in the composition for a functional layer and that the preferred ratio of each component is the same as the preferred ratio of the component in the composition for a functional layer.
• Examples of methods by which the functional layer may be formed on the substrate using the composition for a functional layer include, but are not specifically limited to:
• a functional layer may be formed on just one side of the substrate, or functional layers may be formed on both sides of the substrate.
• a known releasable substrate can be used as the releasable substrate without any specific limitations.
• method (1) is preferable due to ease of controlling the thickness of the functional layer.
• method (1) may, for example, include a step of applying the composition for a functional layer onto the substrate (application step) and a step of drying the composition for a functional layer that has been applied onto the substrate to form a functional layer (functional layer formation step).
• composition for a functional layer examples include, but are not specifically limited to, doctor blading, reverse roll coating, direct roll coating, gravure coating, extrusion coating, and brush coating.
• the composition for a functional layer on the substrate can be dried by any commonly known method in the functional layer formation step without any specific limitations.
• the drying method may be drying by warm, hot, or low-humidity air; drying in a vacuum; or drying by irradiation with infrared light, electron beams, or the like.
• the drying temperature is preferably not lower than 50°C and not higher than 150°C, and the drying time is preferably not less than 1 minute and not more than 30 minutes.
• composition for a functional layer set forth above may be a first composition for a functional layer that contains the particulate polymer (X) and the particulate polymer (Y) but does not contain non-conductive heat-resistant particles or may be a second composition for a functional layer that further contains non-conductive heat-resistant particles in addition to the particulate polymer (X) and the particulate polymer (Y).
• the first composition for a functional layer is used to form a functional layer on a substrate, it is possible to obtain an adhesive layer as the functional layer.
• non-conductive heat-resistant particles to the first composition for a functional layer serving as a binder composition, it is possible to produce the second composition for a functional layer that further contains non-conductive heat-resistant particles.
• the second composition for a functional layer is used to form a functional layer on a substrate
• a single layer also referred to as a "heat-resistant adhesive layer”
• a function as a heat-resistant layer that increases heat resistance of the substrate
• a function as an adhesive layer that strongly adheres members to each other it is possible to obtain, as the functional layer, a single layer (also referred to as a "heat-resistant adhesive layer") that can simultaneously display a function as a heat-resistant layer that increases heat resistance of the substrate and a function as an adhesive layer that strongly adheres members to each other.
• a substrate (laminate) that includes a functional layer formed using the second composition for a functional layer as described above has high producibility because production with reduced man-hours and time is possible as compared to a conventional substrate that includes a heat-resistant layer and an adhesive layer.
• a functional layer that is formed using the second composition for a functional layer containing non-conductive heat-resistant particles normally includes a layer formed of the non-conductive heat-resistant particles (hereinafter, referred to as a "non-conductive heat-resistant particle layer"). Moreover, the non-conductive heat-resistant particle layer normally has a plurality of the non-conductive heat-resistant particles stacked on one another in a thickness direction of the functional layer.
• the thickness of the non-conductive heat-resistant particle layer is preferably 0.5 ⁇ m or more, more preferably 0.8 ⁇ m or more, and even more preferably 1 ⁇ m or more, and is preferably 6 ⁇ m or less, more preferably 5 ⁇ m or less, and even more preferably 4 ⁇ m or less.
• the functional layer has extremely good heat resistance.
• the thickness of the non-conductive heat-resistant particle layer is not more than any of the upper limits set forth above, ion conductivity of the functional layer can be ensured, and output characteristics of an electrochemical device including the functional layer can be improved.
• the thickness of the non-conductive heat-resistant particle layer can be adjusted by altering application conditions in the previously described application step, for example.
• a ratio of the volume-average particle diameter of the particulate polymer (X) relative to the thickness of the non-conductive heat-resistant particle layer (volume-average particle diameter of particulate polymer (X)/thickness of non-conductive heat-resistant particle layer) is preferably 0.8 or more, more preferably 1.2 or more, even more preferably 1.5 or more, and further preferably 1.8 or more, and is preferably 10 or less, more preferably 6 or less, even more preferably 4 or less, and further preferably 3.3 or less.
• the ratio of the volume-average particle diameter of the particulate polymer (X) relative to the thickness of the non-conductive heat-resistant particle layer is not less than any of the lower limits set forth above, this makes it easier for the particulate polymer (X) to protrude relative to the surface of the non-conductive heat-resistant particles at a thickness direction surface of the functional layer, and thus can further improve adhesiveness of the functional layer.
• the ratio of the volume-average particle diameter of the particulate polymer (X) relative to the thickness of the non-conductive heat-resistant particle layer is not more than any of the upper limits set forth above, shedding of the particulate polymer (X) during application of the composition for a functional layer onto the substrate can be inhibited, and a uniform functional layer can be formed.
• the presently disclosed electrochemical device includes the presently disclosed laminate for an electrochemical device.
• An electrochemical device such as set forth above can display excellent electrochemical characteristics (for example, output characteristics and cycle characteristics).
• the presently disclosed electrochemical device should include at least the presently disclosed laminate and thus may also include constituent elements other than the presently disclosed laminate so long as the effects according to the present disclosure are not noticeably lost.
• the presently disclosed electrochemical device may be, but is not specifically limited to, a lithium ion secondary battery or an electric doublelayer capacitor, and is preferably a lithium ion secondary battery.
• a lithium ion secondary battery according to the present disclosure includes the presently disclosed laminate set forth above. More specifically, the lithium ion secondary battery includes a positive electrode, a negative electrode, a functional layer-equipped separator (presently disclosed laminate) in which a functional layer is formed on a separator substrate, and an electrolyte solution.
• a functional layer may be formed on just one side of the separator substrate, or functional layers may be formed on both sides of the separator substrate.
• the functional layer is formed on the separator substrate in the following example, the functional layer may be formed on an electrode substrate.
• the functional layer enables strong adhesion between the positive electrode and the separator substrate and/or between the negative electrode and the separator substrate in the electrolyte solution. Consequently, widening of the distance between electrode plates of the electrodes in accompaniment to repeated charging and discharging is inhibited, and good battery characteristics such as cycle characteristics are obtained. Moreover, in a case in which the functional layer contains non-conductive heat-resistant particles, heat resistance of the separator in the lithium ion secondary battery can be improved through the functional layer.
• this lithium ion secondary battery requires less time for separator production and can be produced with high productivity as compared to a case in which a conventional separator including a heat-resistant layer and an adhesive layer is used.
• Known positive electrodes, negative electrodes, and electrolyte solutions that are used in lithium ion secondary batteries can be used as the previously mentioned positive electrode, negative electrode, and electrolyte solution.
• the electrodes can each be an electrode that is obtained by forming an electrode mixed material layer on a current collector.
• the current collector may be made of a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum. Of these metal materials, the current collector for the negative electrode is preferably made of copper. Moreover, the current collector for the positive electrode is preferably made of aluminum.
• the electrode mixed material layer can be a layer that contains an electrode active material and a binder.
• the functional layer-equipped separator can be produced by, for example, forming a functional layer on a separator substrate using the method of forming a functional layer that was described above.
• the separator substrate is not specifically limited and can be any of those described in JP2012-204303A , for example.
• a microporous membrane made of polyolefinic resin polyethylene, polypropylene, polybutene, or polyvinyl chloride
• such a membrane can reduce the total thickness of the functional layer-equipped separator, which increases the ratio of electrode active material in the lithium ion secondary battery, and thereby increases the volumetric capacity of the lithium ion secondary battery.
• the electrolyte solution is normally an organic electrolyte solution obtained by dissolving a supporting electrolyte in an organic solvent.
• the supporting electrolyte may, for example, be a lithium salt in the case of a lithium ion secondary battery.
• lithium salts that may be used include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi, (CF 3 SO 2 ) 2 NLi, and (C 2 F 5 SO 2 )NLi.
• LiPF 6 , LiClO 4 , and CF 3 SO 3 Li are preferable as they readily dissolve in solvents and exhibit a high degree of dissociation.
• One electrolyte may be used individually, or two or more electrolytes may be used in combination.
• lithium ion conductivity tends to increase when a supporting electrolyte having a high degree of dissociation is used. Therefore, lithium ion conductivity can be adjusted through the type of supporting electrolyte that is used.
• organic solvent used in the electrolyte solution is not specifically limited so long as the supporting electrolyte can dissolve therein.
• organic solvents that can suitably be used in a lithium ion secondary battery, for example, include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (ethyl methyl carbonate (EMC)), and vinylene carbonate; esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide.
• DMC dimethyl carbonate
• EC ethylene carbonate
• DEC diethyl carbonate
• PC propylene carbonate
• BC butylene carbonate
• EMC methyl ethyl carbonate
• vinylene carbonate
• organic solvents may be used.
• carbonates are preferable due to having high permittivity and a wide stable potential region.
• lithium ion conductivity tends to increase when an organic solvent having a low viscosity is used. Therefore, lithium ion conductivity can be adjusted through the type of organic solvent that is used.
• the concentration of the electrolyte in the electrolyte solution can be adjusted as appropriate. Furthermore, known additives may be added to the electrolyte solution.
• the lithium ion secondary battery that is an example of the presently disclosed electrochemical device can be produced by, for example, stacking the above-described positive electrode and negative electrode with the functional layer-equipped separator (presently disclosed laminate) in-between, performing rolling, folding, or the like of the resultant stack, as necessary, to place the stack in a battery container, injecting the electrolyte solution into the battery container, and sealing the battery container.
• an expanded metal; an overcurrent preventing device such as a fuse or a PTC device; or a lead plate may be provided in the battery container as necessary.
• the shape of the battery may be a coin type, a button type, a sheet type, a cylinder type, a prismatic type, a flat type, or the like, for example.
• the proportion constituted in the polymer by a structural unit formed through polymerization of a given monomer is normally, unless otherwise specified, the same as the ratio (charging ratio) of the given monomer among all monomers used in polymerization for forming the polymer.
• methods described below were used for measurement of volume-average particle diameter, glass-transition temperature, degree of swelling in electrolyte solution, thickness of a non-conductive heat-resistant particle layer, ratio of volume-average particle diameter of a particulate polymer (X) relative to thickness of a non-conductive heat-resistant particle layer, and volume ratio of inorganic particles and a particulate polymer (X).
• methods described below were used for measurement and evaluation of air permeability, heat resistance, dry adhesiveness, and wet adhesiveness of a functional layer, and output characteristics and cycle characteristics of a secondary battery.
• Particulate polymers (X) and particulate polymers (Y) produced in the examples and comparative examples were each taken as a measurement sample.
• the measurement sample was weighed into an aluminum pan in an amount of 10 mg and was measured by a differential scanning calorimeter (EXSTAR DSC6220 produced by SII NanoTechnology Inc.) under conditions prescribed in JIS Z8703 with a measurement temperature range of -100°C to 500°C and a heating rate of 10°C/min and with an empty aluminum pan as a reference to obtain a differential scanning calorimetry (DSC) curve.
• EXSTAR DSC6220 produced by SII NanoTechnology Inc.
• Particulate polymers (X) produced in the examples and comparative examples were each taken as a measurement sample.
• the measurement sample was weighed out in an amount equivalent to 0.1 g, was taken into a beaker, and 0.1 mL of alkylbenzenesulfonic acid aqueous solution (DRIWEL produced by FUJIFILM Corporation) as a dispersant was added thereto.
• DRIWEL alkylbenzenesulfonic acid aqueous solution
• 10 mL to 30 mL of a diluent ISOTON II produced by Beckman Coulter, Inc.
• 3 minutes of dispersing was performed by an ultrasonic disperser 20 W (Watt).
• a particle size analyzer (Multisizer produced by Beckman Coulter, Inc.) was used to determine the volume-average particle diameter of the measurement sample under conditions of an aperture diameter of 20 ⁇ m, a medium of ISOTON II, and a measured particle count of 100,000.
• the volume-average particle diameter of each particulate polymer (Y) produced in the examples was measured by laser diffraction. Specifically, a produced water dispersion containing a binder (adjusted to a solid content concentration of 0.1 mass%) was used as a sample. In a particle diameter distribution (by volume) measured using a laser diffraction particle size analyzer (LS-230 produced by Beckman Coulter, Inc.), the particle diameter D50 at which cumulative volume calculated from a small diameter end of the distribution reached 50% was taken to be the volume-average particle diameter.
• the volume-average particle diameter of non-conductive heat-resistant particles was taken to be the particle diameter (D50) at which, in a particle diameter distribution (by volume) measured by laser diffraction, cumulative volume calculated from a small diameter end of the distribution reached 50%.
• a water dispersion containing a particulate polymer (X) produced in each example or comparative example was loaded into a petri dish made of polytetrafluoroethylene and was dried under conditions of 48 hours at 25°C to prepare a powder. Approximately 0.2 g of the obtained powder was pressed at 200°C and 5 MPa for 2 minutes to obtain a film. The obtained film was cut to 1 cm-square to obtain a test specimen. The mass WO of the test specimen was measured.
• test specimen described above was immersed in electrolyte solution at 60°C for 72 hours. Thereafter, the test specimen was withdrawn from the electrolyte solution, electrolyte solution on the surface of the test specimen was wiped off, and the mass W1 of the test specimen after the immersion test was measured.
• the thickness of a non-conductive heat-resistant particle layer was calculated from an SEM image obtained by observing a cross-section of a functional layer-equipped separator using a field emission scanning electron microscope (FE-SEM). Note that the thickness of the non-conductive heat-resistant particle layer was taken to be the distance from the surface of a separator substrate where a slurry composition had been applied to a non-conductive heat-resistant particle furthest separated therefrom in a perpendicular direction.
• FE-SEM field emission scanning electron microscope
• a functional layer-equipped separator produced in each example or comparative example was cut out as a square of 12 cm TD (width direction) ⁇ 12 cm MD (length direction), and then a cross was drawn at the center of the square by drawing lines of 10 cm in length in the TD and MD so as to obtain a test specimen.
• the test specimen was placed in a 150°C constant-temperature tank and was left for 1 hour. Thereafter, ⁇ (length of line before being left (10 cm) - length of line after being left)/(length of line before being left (10 cm)) ⁇ ⁇ 100[%] was calculated with respect to each of the lines drawn in the TD and MD as a heat shrinkage rate and was evaluated by the following standard. A smaller heat shrinkage rate indicates that the functional layer has better heat resistance.
• a negative electrode and a functional layer-equipped separator (including functional layers at both sides) produced in each example or comparative example were each cut out as 10 mm in width and 50 mm in length.
• the negative electrode and the separator were stacked and were pressed by a flat-plate press with a temperature of 80°C and a load of 1 kN for 10 seconds to obtain a test specimen.
• This test specimen was placed with the surface at the current collector-side of the negative electrode facing downward, and cellophane tape was affixed to the surface of the electrode. Tape prescribed by JIS Z1522 was used as the cellophane tape. Moreover, the cellophane tape was fixed to a horizontal test stage in advance.
• the stress when the separator was peeled off by pulling one end of the separator vertically upward at a pulling speed of 50 mm/min was measured.
• the stress was measured three times in total.
• An average value of the three obtained stress values was determined as the peel strength (N/m) and was evaluated by the following standard as the adhesiveness (dry adhesiveness) between an electrode and a separator via a functional layer. A larger peel strength indicates better dry adhesiveness.
• a positive electrode and a functional layer-equipped separator (including functional layers at both sides) produced in each example or comparative example were each cut to 50 mm in length and 10 mm in width.
• the cut positive electrode and separator were then overlapped and stacked.
• the resultant laminate was pressed at a pressing rate of 30 m/min by roll pressing with a temperature of 25°C and a load of 10 kN/m to obtain a test specimen.
• This test specimen was then immersed in electrolyte solution having a temperature of 60°C for 72 hours.
• EC ethylene carbonate
• DEC diethyl carbonate
• the test specimen was removed from the electrolyte solution, and electrolyte solution on the surface of the test specimen was wiped off.
• the test specimen was pressed once again under conditions of 2 minutes at 1 MPa and 50°C.
• the re-pressed test specimen was placed with the surface at the current collector-side of the positive electrode facing downward, and cellophane tape (tape prescribed by JIS Z1522) was affixed to the surface of the positive electrode.
• the cellophane tape was fixed to a horizontal test stage in advance.
• the stress when the separator was peeled off by pulling one end of the separator vertically upward at a pulling speed of 50 mm/min was measured.
• a total of three measurements were made in this manner.
• a laminate of a negative electrode and a separator was obtained, and this laminate was pressed to obtain a test specimen in the same manner as described above.
• a re-pressed test specimen was obtained, and the stress after immersion in electrolyte solution was measured a total of three times.
• peel strength N/m
• adhesiveness wet adhesiveness
• a lithium ion secondary battery produced in each example or comparative example was constant-current constant-voltage (CCCV) charged to 4.3 V in an atmosphere having a temperature of 25°C for cell preparation.
• the prepared cell was discharged to 3.0 V by 0.2C and 1.5C constant-current methods, and the electric capacity was determined.
• a lithium ion secondary battery produced in each example or comparative example was left at rest at a temperature of 25°C for 5 hours after injection of electrolyte solution.
• the lithium ion secondary battery was charged to a cell voltage of 3.65 V by a 0.2C constant-current method at a temperature of 25°C and was then subjected to 12 hours of aging at a temperature of 60°C.
• the lithium ion secondary battery was subsequently discharged to a cell voltage of 3.00 V by a 0.2C constant-current method at a temperature of 25°C.
• CC-CV charging upper limit cell voltage 4.20 V
• CC discharging was performed to 3.00 V by a 0.2C constant-current method. This charging and discharging at 0.2C was repeated three times.
• the lithium ion secondary battery was subjected to 200 cycles of a charge/discharge operation with a cell voltage of 4.20 V to 3.00 V and a charge/discharge rate of 1.0C in an environment having a temperature of 25°C.
• the discharge capacity of the 1 st cycle was defined as X1 and the discharge capacity of the 200 th cycle was defined as X2.
• a monomer composition (X1) was produced by mixing 61.8 parts of styrene as an aromatic monovinyl monomer, 13 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 25 parts of glycidyl methacrylate as a reactive monomer A, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.
• a colloidal dispersion liquid (X1) containing magnesium hydroxide as a metal hydroxide was produced by gradually adding an aqueous solution of 7.0 parts of sodium hydroxide dissolved in 50 parts of deionized water to an aqueous solution of 10.0 parts of magnesium chloride dissolved in 200 parts of deionized water under stirring.
• a particulate polymer (X1) was produced by suspension polymerization as a particulate polymer (X). Specifically, the monomer composition (X1) obtained as described above was added to the colloidal dispersion liquid (X1) containing magnesium hydroxide, was further stirred therewith, and then 3.0 parts of t-butyl peroxy-2-ethylhexanoate (PERBUTYL O produced by NOF Corporation) was added as a polymerization initiator to yield a mixture.
• PERBUTYL O t-butyl peroxy-2-ethylhexanoate
• the obtained mixture was subjected to 1 minute of high-shear stirring at a rotation speed of 12,000 rpm using an inline emulsifying/dispersing device (CAVITRON produced by Pacific Machinery & Engineering Co., Ltd.) so as to form droplets of the monomer composition (X1) in the colloidal dispersion liquid containing magnesium hydroxide.
• CAVITRON produced by Pacific Machinery & Engineering Co., Ltd.
• the magnesium hydroxide-containing colloidal dispersion liquid in which droplets of the monomer composition (X1) had been formed was loaded into a reactor, the temperature was raised to 90°C, and a polymerization reaction was performed for 5 hours.
• the resultant dispersion liquid was subjected to 2 hours of treatment under reduced pressure at 90°C using an evaporator to perform purification and yield a water dispersion containing the particulate polymer (X1).
• the water dispersion containing the particulate polymer (X1) was stirred while sulfuric acid was added dropwise at room temperature (25°C) so as to perform acid washing until the pH reached 6.5 or lower.
• the glass-transition temperature and volume-average particle diameter of the obtained particulate polymer (X1) were measured. The results are shown in Table 1.
• a particulate polymer (Y1) was produced as a particulate polymer (Y) as described below.
• a reactor including a stirrer was supplied with 70 parts of deionized water, 0.15 parts of sodium lauryl sulfate (EMAL ® 2F (EMAL is a registered trademark in Japan, other countries, or both) produced by Kao Corporation) as an emulsifier, and 0.5 parts of ammonium persulfate as a polymerization initiator.
• the gas phase was purged with nitrogen gas, and the temperature was raised to 60°C.
• a monomer composition (Y1) was produced in a separate vessel by mixing 50 parts of deionized water, 1.0 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 90 parts of n-butyl acrylate as a (meth)acrylic acid alkyl ester monomer, 5 parts of acrylonitrile as a nitrile group-containing monomer, 4 parts of acrylamide and 0.8 parts of methacrylic acid as reactive monomers B, and 0.2 parts of allyl methacrylate as a cross-linkable monomer.
• the obtained monomer composition (Y1) was continuously added into the above-described reactor including a stirrer over 4 hours to perform polymerization. The reaction was carried out at 60°C during the addition. Once the addition was complete, a further 3 hours of stirring was performed at 70°C, and then the reaction was ended to yield a water dispersion containing the particulate polymer (Y1) as an acrylic polymer.
• the obtained particulate polymer (Y1) had a volume-average particle diameter of 0.15 ⁇ m and a glass-transition temperature of -40°C.
• a binder composition was obtained by adding 0.2 parts of sodium dodecylbenzenesulfonate (NEOPELEX G-15 produced by Kao Corporation) as an emulsifier, 1.5 parts of carboxymethyl cellulose as a thickener, and 0.5 parts of 1,2-benzo-4-isothiazolin-3-one as an amine compound to 100 parts of the particulate polymer (X1), and then further adding and mixing 108 parts in terms of solid content of the water dispersion containing the particulate polymer (Y1).
• sodium dodecylbenzenesulfonate NEOPELEX G-15 produced by Kao Corporation
• alumina Alumina (AKP3000 produced by Sumitomo Chemical Co., Ltd.; volume-average particle diameter: 0.7 ⁇ m) as non-conductive heat-resistant particles
• the mixing ratio of the non-conductive heat-resistant particles and the particulate polymer (X1) in the resultant slurry composition was adjusted to 90: 10 as a volume ratio (non-conductive heat-resistant particles:particulate polymer (X1)).
• the mixing ratio of the non-conductive heat-resistant particles and the particulate polymer (X1) in the slurry composition was adjusted to 360: 10 as a mass ratio (non-conductive heat-resistant particles:particulate polymer (X1)).
• a microporous membrane made of polyethylene (thickness: 12 ⁇ m) was prepared as a separator substrate.
• the slurry composition obtained as described above was applied onto one side of the separator substrate by bar coating.
• the separator substrate with the slurry composition applied thereon was dried at 50°C for 1 minute to form a functional layer.
• the same operations were performed with respect to the other side of the separator substrate to produce a functional layer-equipped separator (laminate) that included functional layers of 2.0 ⁇ m each in thickness at both sides of the separator substrate.
• the mixture containing the binder for a negative electrode mixed material layer was adjusted to pH 8 through addition of 5% sodium hydroxide aqueous solution and was subsequently subjected to thermal-vacuum distillation to remove unreacted monomer. Thereafter, the mixture was cooled to 30°C or lower to yield a water dispersion containing the target binder for a negative electrode mixed material layer.
• the post-pressing positive electrode produced as described above was cut out as a rectangle of 49 cm ⁇ 5 cm and was placed with the surface at the positive electrode mixed material layer-side facing upward.
• the functional layer-equipped separator was cut out as 120 cm ⁇ 5.5 cm and was arranged on the positive electrode mixed material layer such that the positive electrode was positioned at one longitudinal direction side of the functional layer-equipped separator.
• the post-pressing negative electrode produced as described above was cut out as a rectangle of 50 cm ⁇ 5.2 cm and was arranged on the functional layer-equipped separator such that the surface at the negative electrode mixed material layer-side thereof was facing toward the functional layer-equipped separator and such that the negative electrode was positioned at the other longitudinal direction side of the functional layer-equipped separator.
• the particulate polymer (X2) was produced by performing operations in the same way as in production of the particulate polymer (X1) of Example 1 with the exception that a monomer composition (X2) was used instead of the monomer composition (X1).
• the monomer composition (X2) was produced by mixing 66.8 parts of styrene as an aromatic monovinyl monomer, 23 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 10 parts of glycidyl methacrylate as a reactive monomer A, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.
• the particulate polymer (X3) was produced by performing operations in the same way as in production of the particulate polymer (X1) of Example 1 with the exception that a monomer composition (X3) was used instead of the monomer composition (X1).
• the monomer composition (X3) was produced by mixing 71.8 parts of styrene as an aromatic monovinyl monomer, 26 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 2 parts of glycidyl methacrylate as a reactive monomer A, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.
• a water dispersion containing the particulate polymer (Y2) was produced by performing operations in the same way as in production of the water dispersion containing the particulate polymer (Y1) of Example 1 with the exception that a monomer composition (Y2) was used instead of the monomer composition (Y1).
• the monomer composition (Y2) was produced by mixing 50 parts of deionized water, 1.0 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate as a (meth)acrylic acid alkyl ester monomer, 1 part of N-isopropylacrylamide and 1 part of methacrylic acid as reactive monomers B, 2 parts of acrylonitrile as a nitrile group-containing monomer, and 2 parts of allyl methacrylate as a cross-linkable monomer.
• a water dispersion containing the particulate polymer (Y3) was produced by performing operations in the same way as in production of the water dispersion containing the particulate polymer (Y1) of Example 1 with the exception that a monomer composition (Y3) was used instead of the monomer composition (Y1).
• the monomer composition (Y3) was produced by mixing 50 parts of deionized water, 1.0 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate as a (meth)acrylic acid alkyl ester monomer, 1 part of maleic anhydride and 1 part of methacrylic acid as reactive monomers B, 2 parts of acrylonitrile as a nitrile group-containing monomer, and 2 parts of allyl methacrylate as a cross-linkable monomer.
• a water dispersion containing the particulate polymer (Y4) was produced by performing operations in the same way as in production of the water dispersion containing the particulate polymer (Y1) of Example 1 with the exception that a monomer composition (Y4) was used instead of the monomer composition (Y1).
• the monomer composition (Y4) was produced by mixing 50 parts of deionized water, 1.0 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate as a (meth)acrylic acid alkyl ester monomer, 1 part of N-methylolacrylamide and 1 part of methacrylic acid as reactive monomers B, 2 parts of acrylonitrile as a nitrile group-containing monomer, and 2 parts of allyl methacrylate as a cross-linkable monomer.
• the particulate polymer (X4) was produced by performing operations in the same way as in production of the particulate polymer (X1) of Example 1 with the exception that a monomer composition (X4) was used instead of the monomer composition (X1).
• the monomer composition (X4) was produced by mixing 70.8 parts of styrene as an aromatic monovinyl monomer, 19 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 10 parts of 4-hydroxybutyl acrylate as a reactive monomer A, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.
• the magnesium hydroxide-containing colloidal dispersion liquid in which droplets of the first monomer composition (X7) had been formed was loaded into a reactor, the temperature was raised to 90°C, and a polymerization reaction was performed for 1 hour. After 1 hour, the second monomer composition (X7) was added into the reactor, and a polymerization reaction was performed for a further 5 hours at 90°C.
• the resultant dispersion liquid was subjected to 2 hours of treatment under reduced pressure at 90°C using an evaporator to perform purification and yield a water dispersion containing the particulate polymer (X7).
• the monomer composition (Y5) was produced by mixing 50 parts of deionized water, 1.0 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 30 parts of styrene as an aromatic monovinyl monomer, 69 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 0.5 parts of acrylamide and 0.3 parts of methacrylic acid as reactive monomers B, and 0.2 parts of allyl methacrylate as a cross-linkable monomer.
• a 5 MPa pressure-resistant vessel equipped with a stirrer was charged with 62 parts of 1,3-butadiene, 35 parts of styrene, 1 part of acrylamide and 2 parts of itaconic acid as reactive monomers B, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized water, and 0.5 parts of potassium persulfate as a polymerization initiator. These materials were thoroughly stirred and were then heated to 50°C to initiate polymerization. At the point at which the polymerization conversion rate reached 96%, cooling was performed to quench the reaction to yield a mixture containing the particulate polymer (Y6).
• This mixture was adjusted to pH 8 through addition of 5% sodium hydroxide aqueous solution and was subsequently subjected to thermal-vacuum distillation to remove unreacted monomer. Thereafter, the mixture was cooled to 30°C or lower to yield a water dispersion containing the particulate polymer (Y6).
• the particulate polymer (X9) was produced by performing operations in the same way as in production of the particulate polymer (X1) of Example 1 with the exception that a monomer composition (X9) was used instead of the monomer composition (X1).
• the monomer composition (X9) was produced by mixing 72.8 parts of styrene as an aromatic monovinyl monomer, 24 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 3 parts of acrylamide as a reactive monomer B, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.
• the particulate polymer (Y7) was produced by performing operations in the same way as in production of the water dispersion containing the particulate polymer (Y1) of Example 1 with the exception that a monomer composition (Y7) was used instead of the monomer composition (Y1).
• the monomer composition (Y7) was produced by mixing 50 parts of deionized water, 0.7 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 79 parts of n-butyl acrylate as a (meth)acrylic acid alkyl ester monomer, 15 parts of glycidyl methacrylate and 0.8 parts of methacrylic acid as reactive monomers A, 5 parts of acrylonitrile as a nitrile group-containing monomer, and 0.2 parts of allyl methacrylate as a cross-linkable monomer.
• the particulate polymer (X10) was produced by performing operations in the same way as in production of the particulate polymer (X1) of Example 1 with the exception that a monomer composition (X10) was used instead of the monomer composition (X1).
• the monomer composition (X10) was produced by mixing 72.8 parts of styrene as an aromatic monovinyl monomer, 27 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.
• the particulate polymer (Y8) was produced by performing operations in the same way as in production of the water dispersion containing the particulate polymer (Y1) of Example 1 with the exception that a monomer composition (Y8) was used instead of the monomer composition (Y1).
• the monomer composition (Y8) was produced by mixing 50 parts of deionized water, 1.0 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94.8 parts of n-butyl acrylate as a (meth)acrylic acid alkyl ester monomer, 5 parts of acrylonitrile as a nitrile group-containing monomer, and 0.2 parts of allyl methacrylate as a cross-linkable monomer.
• Example 1 Example 2
• Example 3 Example 4
• Example 5 Example 6
• Chemical composition Reactive monomer unit A (epoxy group-containing monomer unit) GMA [mass%] 25 10 2 25 25 25 Reactive monomer mit A (hydroxy group-containing monomer unit) 4HBA [mass%] - - - - - - - -
• a functional layer having excellent adhesiveness can be formed through the compositions for a functional layer of Examples 1 to 17, which each contain a particulate polymer (X) and a particulate polymer (Y) having a smaller volume-average particle diameter than the particulate polymer (X), and in each of which one of the particulate polymer (X) and the particulate polymer (Y) includes a specific reactive monomer unit A while the other of the particulate polymer (X) and the particulate polymer (Y) includes a specific reactive monomer unit B.
• composition for an electrochemical device functional layer that can form a functional layer having excellent adhesiveness.

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• 2023
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